In recent years, since a semiconductor becomes finer to meet a demand for further high quality semiconductor film, a deposition process of an atomic layer level for alternately supplying two or more kinds of reactive gases is focused. As a material of such reactive gases, a reaction of a metal-containing raw material and a gas containing oxygen or nitrogen is utilized.
The deposition process can be roughly divided in two according to a reaction type. One of them is an ALD (Atomic Layer Deposition), and the other of them is a MOCVD (Metal Organic Chemical Vapor Deposition) in which a cycle-method is applied (for example see patent documents 1 and 2). The aforementioned methods have a basic gas supplying method in common, and therefore an explanation is given by using FIG. 17. FIG. 17(a) is a flowchart, and FIG. 17(b) is a gas supplying timing diagram. In an example shown in the figure, a vaporized metal containing raw material is represented by a raw material A, and the gas containing oxygen or nitrogen is represented by a raw material B.
In a case of the ALD, in step 1, the raw material A is supplied to a substrate and adsorbed on the substrate. In step 2, a residual raw material A is exhausted. In step 3, the raw material B is supplied to the substrate, and the raw material B is allowed to react with the raw material A, to perform deposition. In step 4, the residual raw material B is exhausted. The ALD method is the method of repeatedly perform cycles more than once, with the aforementioned four steps set as one cycle. As is shown in the gas supplying timing of FIG. 17(b), when the raw material A and the raw material B are alternately supplied, exhaustion by purge gas is executed.
In the MOCVD, in which the cycle method is applied, in step 1, the raw material A is supplied to the substrate, which is then thermally decomposed, to perform deposition. In step 2, the residual raw material A is exhausted. In step 3, the raw material B is supplied to the substrate and a film modifying process for a deposited film is performed. In step 4, the residual raw material B is exhausted. The MOCVD method, in which the cycle method is applied, is the method of repeatedly perform cycles more than once, with the aforementioned four steps set as one cycle. As is shown in the gas supplying timing of FIG. 17(b), when the raw material A and the raw material B are alternately supplied, exhaustion by purge gas is executed.
Generally, the raw material A and the raw material B have extremely high reactivity in many cases, and when these raw materials are simultaneously supplied, a foreign matter is generated by vapor-phase reaction and a deposition of a film with deteriorated film quality is generated, thus causing a decline in yield ratio. Therefore, in the aforementioned steps 2 and 4, purge (exhaustion) by evacuation and inert gas is executed, so that the gaseous starting material supplied in the aforementioned previous steps 2 and 4 does not remain. Particularly, a residual gas on the upstream side of the substrate immediately affects a deposition condition of the substrate, and therefore a sufficient exhaustion is required.
However, if it takes long time for exhaustion, although the sufficient exhaustion is enabled, there is a problem that a throughput in productivity is deteriorated.
Also, in a case of the ALD, there is a possibility that a film is deposited all over the area where the raw material in a processing chamber is adsorbed, thus producing particles. Therefore, a contact-gas area of the gaseous starting material is required to be made small as much as possible. Simultaneously, in order to shorten a substitution time of two or more kinds of the starting gases, a flow passage capacity of the gaseous starting material is also required to be made small as much as possible.
Also, a single wafer type apparatus for processing substrates sheet by sheet becomes a main stream as a semiconductor manufacturing device for executing the aforementioned deposition method. In order to form a high quality film with high productivity by using the single wafer type apparatus, gas supply and an exhaustion method are important, from the viewpoint of the aforementioned particles and throughput.
Patent document 1: Japanese Patent Laid Open No. 2003-347298
Patent document 2: Japanese Patent Laid Open No. 2004-158811